Generalized Ellipsometry on Complex Nanostructures and Low-Symmetry Materials

Authors

Alyssa Mock, University of Nebraska-LincolnFollow

First Advisor

Eva Schubert

Second Advisor

Mathias Schubert

Date of this Version

12-2017

Citation

Alyssa Mock, "Generalized Ellipsometry on Complex Nanostructures and Low-Symmetry Materials" (2017). PhD dissertation, University of Nebraska.

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Electrical Engineering, Under the Supervision of Professors Eva Schubert and Mathias Schubert. Lincoln, Nebraska: December, 2017

Copyright 2017 Alyssa Lynn Mock

Abstract

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with monoclinic and triclinic symmetries. A model eigendielectric displacement vector approach is developed, described and utilized to characterize monoclinic materials. Materials are investigated in spectral regions spanning from the far-infrared to the vacuum ultraviolet. Examples are demonstrated for phonon mode determination in cadmium tungstate and yttrium silicate and for band-to-band transitions in gallia (β-Ga₂O₃) single crystals. Furthermore, the anisotropic optical properties of an emerging class of spatially coherent heterostructure materials with nanostructure dimensions are investigated. The so-called anisotropic effective medium approximation for slanted columnar thin films is extended to the concept of slanted columnar heterostructure thin films as well as core-shell heterostructure thin films. Examples include the determination of band-to-band transitions, phonon modes and oxidation properties of cobalt-oxide core shell structures and gas-liquid-solid distribution during controlled adsorption of organic solvents in silicon slanted columnar thin films.

Advisors: Eva Schubert and Mathias Schubert